Radar sensors
HELLA has been manufacturing radar sensors in the 24 GHz narrow-band range for over a decade. Back in 2005, HELLA introduced the first generation of 24 GHz radar sensors. The sensor system is compatible with the now established standard functions of blind spot detection, lane change assistant and rear parking assistance.
The radar sensor senses and evaluates speed, angle and distance information with respect to objects up to 70 meters behind the vehicle. The LFMSK (linear frequency modulation shift keying) method has been used in this application ever since the first generation of devices.
When this method is applied, the distance and relative speed of multiple targets can be measured and determined with just one signal (chirp) whose frequency changes over time.
The third radar generation uses an advanced FM variant whose modulation bandwidth is limited to max. 200 MHz. The system operates at an average transmission power of 13 dBm (EIRP) in a frequency band between 24.05 and 24.25 GHz. The resulting spatial resolution of 0.75 m is suitable for the rear-vehicle functions implemented.
The monopulse method is used for determining angles. The system carries out a phase comparison of the radar reflections across the different receiving paths using specific signal-processing approaches.
The fourth generation of radar sensors integrates an additional safety function ─ the exit assistant. This makes it possible to detect dangerous situations (e.g. passing vehicles) at an early stage before exiting the vehicle as well as warn vehicle occupants.
